592 EXPERIMENT STATION RECORD. tVol. 43 



Analysis of fundamental factors affecting tractor design, O. B. Zimmer- 

 man (Jour. Soc. Automotive Emjin., 7 (1920), Xo. 1, pp. 7-12, figs. 15). — An 

 analysis is given of tlie relation between weight, total and available drawbar 

 pull, plowing speeds, soil resistance, rolling resistance, and slope in their 

 effect upon the design of a tractor. 



Considerable graphic data are presented, which show that the higher the 

 speed the less is the flexibility of the tractor as regards operation on rolling 

 or level land and available drawbar pull. It is shown that the possible ac- 

 complishment in acreage for a given theoretical expenditure of energy is in 

 favor of low speeds, and the advantage of giving considerable attention to re- 

 ducing the rolling resistance on loose or moist soils by every practical means 

 is considered obvious. It is noted that while the resistance of the soil to the 

 plow is noticeably less in loose land, the surface conditions cause the rolling 

 resistance to be greater and the two factors to a certain extent compensate. 



The data further show that " even allowing the full value in fractional 

 plows pulled at all speeds, and even though discount be made for tlie rolling 

 resistance in the lighter lands, so long as a footing is permitted the advantage 

 lies with moderate and low speeds of plowing." 



Modern farm buildings, A. Hopkins {Neio York: Robert M. M-cBride <€ Co., 

 1920, 3. ed., rev. and enl., pp. 237, pis. 62, figs. S5). — This is the third revised 

 and enlarged edition of this book (E. S. R., 31, p. 291; 37, p. 90), containing 

 chapters on the cow barn, dairy, garage, and other farm buildings, and includ- 

 ing plans of farm barns in existence. A final chapter deals with materials of 

 construction. 



Protecting buildings against the white ant, T. E. Snyder {Engin. Nexcs- 

 Rec., 84 (1920), No. 23, pp. 1110-1112, figs. 6).— In a contribution from the Bu- 

 reau of Entomology of the U. S. Department of Agriculture, information is 

 given on the protection of structures, both rural and urban, against termites. 



It is stated that all untreated wood should be completely isolated from the 

 soil, and that in the case of termite-infested frame buildings when once the 

 infested beams are disconnected from the earth the insects will soon dry up and 

 die. It is recommended that in order to prevent the insects from reaching the 

 woodwork of buildings from their nests in the soil, the foundations be entirely 

 of stone, brick, or concrete, including the pillars in basements and cellars. 



Tests to determine the efficiency of coal stoves, J. R. Allen and F. B. 

 Rowley (Jour. Amer. Soe. Heating and Ventilating Engin., 26 (1920), No. 1, 

 pp. 119-126, figs. 4). — Tests conducted at the University of IMinnesota on base- 

 burner coal stoves are reported. 



The results indicate that the best stoves are usually those which have the 

 smallest lengths of cracks and seams. It is noted that in some stoves there are 

 so many cracks and seams that it is almost impossible to make them reasonably 

 air-tight. 



In one test the carbon dioxid was high, showing high efficiency of combustion, 

 and in a second test the carbon dioxid was low, showing a poor state of com- 

 bustion, but the actual total efficiency in the two cases was about the same. 

 This is accounted for by the difference in the stack temperature in the two 

 cases. In the case where the carbon dioxid was high the stack temperature 

 was high, so that the benefit of the better combustion was offset by tlie loss at 

 the stack. In test No. 2 the carbon dioxid and the stack temperature were low, 

 and while there was poor combustion it was offset by less loss at the stack. 



